/Engine/Source/Runtime/Engine/Classes/Components/AudioComponent.h
Allows designers to target a specific Audio Component instance’s sound and set the send level (volume of sound copied) to the indicated Source Bus. If the Source Bus is not already part of the sound’s sends, the reference will be added to this instance’s Override sends. This particular send occurs before the Source Effect processing chain.
void SetSourceBusSendPreEffect ( [USoundSourceBus](API\Runtime\Engine\Sound\USoundSourceBus) * SoundSourceBus, float SourceBusSendLevel )